1. Field of the Invention
This invention relates to a sheet operative member such as a conveyance roller for contacting and conveying sheets by frictional force thereof, and a separation pad for separating sheets, to a sheet conveying apparatus using this member, and to an image processing apparatus such as an electrophotographic photocopier, a printer, a word processor, and a facsimile machine.
2. Description of Related Art
Image forming apparatuses such as printers and photocopiers using one of electrophotographic methods or other recording methods are widely available these days. In accordance with tendency of higher performance and longer duration of the apparatuses, improvements in feeding accuracy and durability in conveyance rollers used in the image forming apparatus are required. Separation pads used for the image forming apparatuses also require in the same manner improvements in separation accuracy and durability.
A conventional conveyance roller 100 is formed, as shown in FIG. 8, of a core metal 101 made of a metal or molded material and a cylindrical rubber portion 102 made of a rubber material such as EPDM (ethylene propylene rubber), CR rubber (chloroprene rubber), silicone rubber, or urethane rubber for contacting a recording sheet and conveying the recording sheet by frictional force. Polishing is made in arrow C or D direction shown in FIG. 8 on a cylindrical surface 102a of the cylindrical rubber portion 102.
A separation pad 103 shown in FIG. 9 is formed of a rubber material such as EPDM, CR rubber, silicone rubber, or urethane rubber in substantially the same manner as the conveyance roller 100 described above and is constituted of a rubber portion 104 in contact with the conveyance roller, and a holder 105 holding the rubber portion 104. Polishing is made in arrow E or F direction shown in FIG. 9 on a rubber surface 104a of the rubber portion 104.
The conventional conveyance roller and the conventional separation pad, however, raised the following problems.
Where the conventional conveyance roller conveys a recording sheet, paper powder generated from surfaces of the recording sheets may attach to the cylindrical surface of the conveyance roller according to an increased conveyance sheet number of the recording sheets, thereby slipping in recording sheet conveyance with lowered frictional force of the conveyance roller, and thereby raising a problem of impaired images and jamming occurrences. To extend the product duration of the apparatus body, users were required to make cleaning, or the apparatuses had a structure that the users can replace the conveyance rollers. As a result, this invited lowered usability and increased costs from additional parts in a structure that the conveyance roller is replaceable.
Where the conventional separation pad separates and conveys the recording sheets, paper powder generated from surfaces of the recording sheets may attach to the surface of the separation pad according to an increased conveyance sheet number of the recording sheets, thereby raising a problem of doubly feeding of the recording sheets due to lowered frictional force of the separation pad. Therefore, substantially the same problem is raised as in the case of the conveyance roller.
This invention is to solve the above problems. It is an object of the invention to provide a sheet operative member such as a conveyance roller or the like avoiding lowered frictional force due to paper powder attachments, realizing highly durable roller members or the like, and having an inexpensive structure of a longer duration with maintenance free and to provide a sheet conveying apparatus and an image processing apparatus using the member.
A preventative structure according to the invention to accomplish the above object is a sheet operative member contacting a sheet and conveying with frictional force the sheet or separating, including a plurality of protrusions on an operative surface with the sheet; and each of the protrusions including: a standing portion standing up from the operative surface; and a spherical portion disposed at a distal end of the standing portion.
Where a conveyance roller is structure of the sheet operative member thus structured, the sheet is conveyed with frictional force from contact with the spherical portions of the protrusions of the conveyance roller. Because the contact between the conveyance roller and the sheet is at the spherical portion at the distal end of the protrusion, paper powder or the like generated from the sheet surfaces is not attached to the spherical portions of the protrusions but deposited in an attaching manner on a circumferential surface of the conveyance roller. This realizes a conveyance roller having property of stable conveyance and high durability. The same advantages can be provided in a case where the sheet operative member is used as a separation pad.
According to the invention, where fine protrusions described above are formed to the sheet operative member, a sheet apparatus is hardly affected from paper powder or the like generated from the sheet surfaces and can enjoy a stable sheet processing performance. Therefore, where structured in use of the sheet operative member described above, the sheet apparatus such as a sheet conveying apparatus can be provided with maintenance free and inexpensive costs.